module adder4(A,B,CI,SUM,CO);
	input [3:0] A;
	input [3:0] B;
	input CI;
	output [3:0] SUM;
	output CO;
	wire c1, c2, c3;

	fulladder1 instance1(A[0],B[0],CI,SUM[0],c1);
	fulladder1 instance2(A[1],B[1],c1,SUM[1],c2);
	fulladder1 instance3(A[2],B[2],c2,SUM[2],c3);
	fulladder1 instance4(A[3],B[3],c3,SUM[3],CO);

endmodule
